At http://phys.org/print386441561.html … we learn that recent hyperthermal activity may explain the bright spots on the asteroid Ceres. This is interesting in as much as it might not weigh against Ceres being an inactive comet (or a former comet but now an asteroid). Having the ability to outgas is a feature of comets – but there the resemblance may end as thermal activity seems to have produced sodium carbonate (the white stuff that the spot is made from).
The study was published in Nature (June 2016) and this is where the sodium carbonate theory is aired. They also say that the crater has a dome like structure in the centre nwhich will probably interest EU people. Sodium carbonate is a form of salt that is also found on Earth – in hydrothermal environments. The material appears to have come from the interior of Ceres we are told, the upwelling indicating temperatures inside were much hotter that previously surmised. In other words liquid water may exist beneath the surface of Ceres. Once water had upwelled it could then have evaporated leaving behind the scum of sodium carbonate.
In addition the team has found evidence of clays containing ammonia – another feature associated with comets and indeed, water in the solar system appears to be fairly common – and comets must also contain it. It is also intriguing that ammonia, sodium carbonate and sodium biocarbonate have been detected in the plumes of Enceladus, an icy mopon of Saturn known for its geysers erupting from fissures on its surface. Another discovery which may tell us something of the structure of comets and asteroids is that the largest crater on Ceres was more than one mile deep relative to the surrounding terrain. They do not seem to have deformed even though it is said that some of them are billions of years of age. However, what is important is that we can take the dates with a pinch of sodium carbonate but it tells us that the sub surface of Ceres is no more than 40 per cent ice by volume and the 60 per cent seems to be a mixture of rock and low density materials such as clathrates (chemical compounds of the kind detected on comets). See also http://dawn.jpl.nasa.gov/news/news-detail.html?id=6547